AM technology has been widely used in electronic article surveillance (EAS) for over twenty years. The original U.S. Pat. No. 4,510,489 disclosed that some of amorphous materials have high magnetic-elastic coupling coefficient, led to strong resonating signal, and used this principle successfully applied these materials into commercial anti-theft system (AM system), such as large supermarket's anti-theft system. AM system includes detector, deactivator, and anti-theft AM markers. There are two types of anti-theft AM markers currently: anti-theft hard tags and anti-theft soft labels. Former uses the amorphous as resonators, uses permanent magnetic materials (such as bonded ferrite magnets, rare-earth bonded magnets or sintered magnets) as bias. This type of markers cannot be deactivated, which is used inside the store repeatedly. Later also uses amorphous as resonators, conventionally a semi-hard magnetic material (such as DC coercivity 10-55 Oe) as bias, or a soft magnetic material with DC coercivity less than 10 Oe used as bias, by same inventor on another invention recently. This type of anti-theft AM marker, (will be called in short as “AM label” or “label” in following) can be repeatedly deactivating or activating. After being deactivated by a deactivator, the label attached to paid merchandise will no longer set off the alarm when it is leaving detector installed at the store gate.
At present, the resonator width of anti-theft markers is generally 6 mm (so far, there are not any commercial AM markers using resonator width below 6 mm). The conventional notion is that the narrower resonator will not make practical AM labels with acceptable detection performance. Thus, the bias width and glue tape area cannot be further reduced with conventional resonator width. Any technical inventions to reduce material costs will have a big achievable economic benefit because of the large amount of AM labels consumed in multiple billions of pieces annually in worldwide market.
The resonators are made of expensive alloys containing Ni or Co (such as FeNiMoB resonators, FeNiCoSiB resonators). The bias alloys also use expensive Ni. To prevent the AM labels from being peeled off easily by shoplifters, due to unavoidable label's raised shape of the hollow resonator house, the double tape has to be made of expensive glue with thicker layer and higher affinity. Wider resonator and wider bias and bigger bottom for double tape glue area led to higher raw material costs. Narrower AM labels can reduce the raw material costs significantly. More important goal is to extend AM label application fields: the stores have some finer or slimmer merchandise, or the area on the package allowed for placement of the AM label without covering important product information or barcode information etc. is smaller, therefore the stores hope to have a narrower AM label for effectively protection. Furthermore, narrower AM label, compared to conventional labels, looks more exquisite to be favored by stores.